In order to protect data, nowadays, data storage device can be disposed with a means of write protection. By the means of write protection, the important data in the data storage device can prevent to be infected by a virus or overwritten.
In the means of previous write protection, a physical write protection switch (WP switch) is disposed on a side of a housing of the data storage device, for example, memory card. It can be decided whether the data storage device is allowed to be written by switching the position of the WP switch.
Alternatively, a write protection function is disposed in a firmware of a controller of the data storage device. When a host wants to perform a write protection process for the data storage device, it may send a WP # command to the data storage device. After the controller of the data storage device receives the WP # command, the write protection process will be started according to the WP # command, so that the data can be inhibited to write into the data storage device.
Different from the means of the previous two write protection, the present invention provides a novelty write protection circuit applied to the data storage device, the write protection circuit of the present invention is having a means of unrecoverable write protection, the data storage device will be permanently inhibited to be written when the unrecoverable write protection of the write protection circuit is be started, which is the object to be achieved by the present invention.